Biodistribution of 99mTc-Macroaggregated Albumin (MAA)

What is another name for MAA?

99mTc-Labeled Human Serum Albumin Particles

What is 99mTc-MAA used for?

• Lung Perfusion Imaging

• Lung Shunt

What is the particle size?

10-90 um (Capillary-Level Embolization)

What is the physical half-life?

6 hours

What is the way of administration of MAA?

Intravenous Injection

What is the distribution of MAA

Entrapped in Pulmonary capillaries

What is the metabolism?

Gradual breakdown by reticuloendothelial system

How is excreted?

Renal and Hepatobiliary over time

What is the pharmacodynamics of MAA

Particle embolization in pulmonary arterioles

• Reflects regional blood flow in lungs

• Used with ventilation agents to assess V/Q mismatch

• No active transport or receptor binding involved

What is the normal biodistribution for MAA

• Lungs

• Liver, spleen (Due to particle shunting or aggregation)

• Kidneys and Bladder

• Abnormal uptake can indicate right-to-left shunt

What is the critical organ for MAA?

• Lungs (receive most radiation)

• Liver and Spleen (If shunting or abnormal distribution)

What are the factors affecting biodistribution?

• Particle size and number

• Cardiac output and Pulmonary perfusion

• Right-to-left shunt (e.g., PFO, AVM)

• Injection technique (e.g., avoid bolus in shunting)